George writes:

Dilute your "real" TSP heavily and throw it on the grass. It's not banned
because it's toxic, just the reverse - it's fertilizer.

As I recall, the problem came with sewage discharges into waterways, which then
had so much algae bloom that the water no longer held oxygen for fish.

Charlie Self

"If our democracy is to flourish, it must have criticism; if our government is
to function it must have dissent."
Henry Commager